Friday could be quite an interesting weather day across Illinois as a late-season storm moves northeast across the area bring a flood of warm, moist and unstable air on its southerly flank in contact with cold air being drawn in from the north and northeast.
The storm will produce heavy snow to its north and potentially severe thunderstorms to its south. The Chicago metro area lies in the battle zone between snow and severe thunderstorms.
Precipitation should begin as rain in the Chicago area by noon Friday but quickly change to heavy wet snow in north central Illinois by early afternoon and in the north and west portions of the Chicago area by early afternoon with accumulation of 6 inches or more possible. The rain will gradually change to snow over the res tof the metro area from northwest to southeast by late afternoon and early evening with somewhat lesser accumulation.
The far south and southeast portions of the Chicago Metro area will like closer to the warm air being drawn north into the storm and are prime candidates for thunderstorms which could become severe.
The Storm Prediction Center in Norman, Oklahoma has outlook much of downstate Illinois and Indiana for severe weather.